Two-dimensional carbides/nitrides, typically called MXenes, are an emerging member of the ever-growing family of two-dimensional materials. The prediction of a ferromagnetic groundstate in chromium-containing MXenes has triggered growing interest in their chemical exfoliation from Cr-based MAX phases. However, the exfoliation poses serious difficulties using standard etching agents such as hydrofluoric acid (HF). Here, we investigate the exfoliability of Cr₂GaC particles by chemical etching with aqueous HF both experimentally and theoretically. Structural and microstructural analyses show that the Cr₂GaC particles decompose into chromium carbide and oxide without the formation of a Cr-based MXene. A thermodynamic analysis based on ab initio electronic structure calculations reveals that the exfoliation of Cr-based MXene from Cr₂GaC by HF-etching is inhibited by more favorable competing reactions. This result confirms the experimental finding and suggests that HF is an unsuitable etching agent for a successful exfoliation of Cr₂GaC.

中文翻译：

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Cr基MAX相颗粒化学剥落的实验和理论研究。

二维碳化物/氮化物（通常称为MXene）是不断增长的二维材料家族中的新兴成员。含铬MXene中铁磁性基态的预测引发了人们对其从Cr基MAX相中化学剥落的兴趣。然而，使用标准的蚀刻剂例如氢氟酸（HF），剥落带来严重的困难。在这里，我们在实验上和理论上研究了用HF水溶液进行化学蚀刻时Cr ₂ GaC颗粒的可剥离性。结构和微观结构分析表明，Cr ₂ GaC颗粒分解为碳化铬和氧化物，而未形成Cr基MXene。从头算起的热力学分析电子结构计算表明，通过更有利的竞争反应可以抑制HF腐蚀从Cr ₂ GaC剥落Cr基MXene 。该结果证实了实验发现，并表明HF对于成功剥离Cr ₂ GaC是不合适的蚀刻剂。